My factory A/C was working well until the compressor clutch burned up. The compressor was fine and the system remained fully charged, so it did not throw crap all through the system. However, I was not able to find and buy just a clutch, so I sent the whole compressor and clutch to Classic Auto Air for a rebuild and new clutch. The compressor was probably getting weak anyway.

All back together, evacuated and holds a good vacuum. Per the manual, I started and added the refrigerant (134a). It took about a half pound, then no more. The 72 has the Super Heat switch which doesn't let the compressor operate at low refrigerant levels, so it doesn't engage the clutch.

Am I doing something wrong? How can I get the system to take the refrigerant?

 

I was thinking maybe I needed to bypass the superheat switch so the compressor would engage.

 

I think you need to jump the thermal fuse for it to charge. You will probably have to replace it after, too. I don't know about the superheat switch. Both those are 72 up things.

 

I think the superheat is a thermal fuse, or similar. On an earlier compressor without the switch, will the compressor engage even when low or out of refrigerant? Obviously, you don't want to run like that for a long period, but to add the refrigerant I suppose it won't hurt.

 

yes

 

You should not need to jumper or bypass anything. The pressure in the can of refrigerant is enough to start the clutch. It takes less than 35psi to start the clutch. I have found that a lot of the time some refrigerant hoses do not actually make contact with the Schrader valve where you are adding the refrigerant. Therefore it's not accessing the system. So make sure you're accessing the system and not just filling up the hose.

John

 

Have you replaced the thermal limiter fuse? It's probably fried....I always buy 2 at a time. You need to push them in all of the way....there's a "tab" that only allows it to be inserted in one direction. I don't want to sound condescending, but you did add the 134 adapter to the low pressure fitting.

 

Ok...I'm not an AC guy, but I have charged a bit. The fuse should be clipped to the bracket. If the system is low...it blows. Dave is most likely right. 72 up is different than charging 72 back. 72 back will swallow, 72 up won't if the fuse is blown. Superheat switch is a different thing. I'm very sure you need to jump the fuse terms to make her swallow. Look at this...old Mitchell book...look at (2) on the last page. Like Dave said buy a couple.

http://vintage.mitchell1.com/PClubDa.../V2D776006.pdf

 

If you have the system pulled into a 500 micron vac it should pull all the freon in without even running the compressor.

Greg

 

UPDATE! I just reread the manual and sure enough, it says to disconnect the Superheat switch. So I thought I had it. But no, it seems I have no power to the compressor.

So I tried to find the problem this morning. Fuse is good, and has power on both sides when A/C turned on at the panel. I have all fan speeds, including the high blower. I have no power at the compressor, no power at the thermal fuse, no power at the superheat switch and no power at the ambient switch. In fact, the ambient switch is totally missing, and has been for years, but the A/C has worked for the past 10 years.

At this point, I'm a little stymied. I'm going to have to find where the power stops. Maybe in the big gaggle of wires behind the distributor. Any ideas?

 

I see in Fig. 1B-3 there is a 30 amp inline fuse between the junction block and the hi blower relay. Is the relay under the dash (where?). Electric wiring is NOT my strong point, but I assume if the fuse was blown, I would have no fan speeds.

Any other inline fuses I'm not thinking about? This is frustrating because it was working correctly until the clutch fried. Then I removed the compressor.

 

Look on the firewall behind distributor, it's the red/black striped wire coming off the distributor. Mine was bad...would only get one speed.....BTW I like the triple white

 

Living in hot Florida, the triple white is very nice. Dark colors, like black seats can blister you in the summer. I used to have a 69 GP and a 69 Vette, both black interiors. Even with the A/C blowing cold, the amount of heat that rolled off the dash kind of cancelled the A/C.

I'll check the red/black wire to see if I have power there. Odd, because everything else works, and it all worked before the clutch burned.

 

Caution - Thread hijack, but similar issues to OP.
My 72 Cutlass compressor clutch will not disengage regardless of dash control switch selections.

I do have a bad fan blower control resistor - fan will not work in high position but I don't think that's causing the compressor to remain on.

Any ideas?

 

The heater/AC control panel has two spring steel switches (kind of like a mechanically actuated relay) that are actuated by the control levers. One of them flips off and on to drive the compressor clutch. That may be stuck in the on position. If you always see power at the ambient temp switch whenever the key is in ACC or RUN (IIRC), then that switch is probably stuck. Need to remove the control panel from the dash (three screws, fiddly but not terribly hard) to take a closer look.

 

I found a broken wire and repaired. After that, with Superheat switch disconnected, the system took the 134A refrigerant.

Now I am getting 20 degree air from the vents on Normal with the fan on lowest speed. We went to a Memorial Service and my wife's feet were ice cold!

I run a totally stock system, except use 134A, and a Crossflow Condenser (from Classic Auto Air). The filter dryer is new and the A6 compressor is rebuilt with a new clutch and a real POA is re-calibrated for 134A. I hear a lot of guys trash the factory system in favor of after market, claiming the factory isn't any good. Aftermarket is great if it is a non-A/C car, but don't be too quick to trash the factory. If you plan to spend what ever it costs for an after market, consider new or rebuilt components for the factory system. Mine is proof that it works. I agree that the new style compressors may use less engine horsepower, but I wouldn't do a wholesale change for a few horses.

 

I merged your new post with the original thread so it shows the end result of your repair. Otherwise it would be another thread with no solution.

 

Thanks Eric. I don't know how to do that, or don't have clearance to do that.